Pressure loaded gear pump



Sept 6, 1966 a. L. RICH PRESSURE LOADED GEAR PUMP 15 Sheets-Sheet 1.

Filed DBC. i7, 1964 r nqvsfwofz. 5e/51012 L. @wie a/W @14,5 A'ffIORNEYs Sept. 6, 1966 B. L. RICH PRESSURE LOADED GEAR PUMP .s Sheets-Sheet fl Filed Dec. L7, 1964 LEVEN-me. B/Zdol L. f/CZ ATTORNEYS Sept. 6, 1966 B. L.. RICH 3,270,680

PRESSURE LOADED GEAR PUMP Filed Dec. 1.7, 1964 5 Sheets-Sheet 5 Wy f /f /l/w A u /f//If/ l ,l/ 7,/ 1 77 .Z2

j a! Il, t /l/'/ m' @YW ,MTUMEYS United States Patent O 3,270,680 PRESSURE LADED GEAR PUMP Belden L. Rich, Kokomo, Intl., assigner to Kingston Products Corporation, Kokomo, Ind., a corporation of Indiana Filed Dec. 17, 1964, Ser. No. 419,064 16 Claims. (Cl. 10S-126) This invention relates generally to pumps and more particularly to a pressure loaded gear pump assembly having a pumping chamber formed therein and including rotary impellers in the chamber for pumping l'luid from an inlet to an outlet side of the chamber. One wall ot' the chamber adjacent one side of the impellers has a relief portion formed therein surrounded by a sealing surface and interposed between the adjacent side faces of the impellers and the relief portion is a llexible end plate forming a pressure recess in said relief portion. An elongated partitioning member or gasket divides the pressure recess into a first portion adjacent the inlet side of the chamber and a second portion adjacent the outlet side. Means are provided to communicate the inlet and outlet portions of the pressure recess with their adjacent sides of the chamber for loading the end plate into engagement with the side faces of the impellers by means of pump generated fluid pressure. The ends of the partitioning member are received respectively in spaced grooves formed in the sealing surface and opening to the end plate for providing a good sealing relation therebetween to minimize or eliminate leakage of fluid past the partitioning member from the second to the first por tion ofthe pressure recess.

It is, therefore, an object of the invention to provide, in a pump of the pressure-loaded end plate type with a pressure recess behind the end plate to load the end plate with pump generated iiud pressure, improved partitioning means in the pressure recess to divide portions thereof to attain better balanced loading of the end plate.

Another object of the invention is to provide an improved pressure loading arrangement for a llexible end plate of a pressure loaded gear pump.

Yet another object of the invention is to provide a positive displacement fluid pump comprising a plurality of shaft mounted rotary members and a lloating pressure loaded end plate for the rotary members with an improved arrangement for isolating various motive surfaces of the end plate to provide increased independency of deflection or movement of such surfaces and to increase the eliiciency of the pump.

Many other features, advantages and additional bjccts of the present invention will become manifest to those versed in the art upon making reference to the de tailed description which follows and the accompanying sheets of drawings in which a preferred structural embodiment of a pump incorporating the principles of the present invention is shown by way of illustrative example.

On the drawings:

FIGURE 1 is a cross-sectional view of a gear pump incorporating the principles of the present invention;

FIGURE 2 is an elevational end view of the pump cover section taken substantially along lines II-Il of FIGURE l;

FIGURE 3 is a sectional view of the pump cover taken along lines lII--Ill of FIGURE 2 and including a fragmentary portion of the pump casing in section;

FIGURE 4 is a fragmentary' sectional view of an interior wall of the pump cover taken along lines IV-IV of FIGURE 2;

FIGURE 5 is a plan view of a flexible wear plate of the invention; and

FIGURE 6 is an enlarged fragmentary cross-sectional 3,270,680 Patented Sept. 6, 1966 ICC view of an end portion of a partitioning member taken along lines VI-VI of FlGURE 2.

As shown in the drawings:

The pump of the present invention is indicated generally at reference numeral 10 and although the principles of the present invention are of general applicability, the particular form of pump herein described is a gear pump which inclues a casing having a center body member ll closed at one side by a closure plate l2 and closed at the opposite side by a cover member 13, suitable alignment studs 14 and fastener members 16 being provided for aligning the casing components and for holding them together in firm assembly.

The center body member 11 is provided with a generally ovoid-shaped pumping chamber or cavity indicated generally at 17 bounded by an outer wall 18. Opposite sides of the chamber 17 form an inlet side 19 and an outlet side 20, and it will be appreciated that suitable side ports as Well as conduits or passageways are provided within the other parts of the pump easing for communicating the inlet and outlet sides of the pumping chamber 17 with the plumbing system of a hydraulic circuit.

A pair of similar gears is rotatably meshed within the pumping chamber 17 and as illustrated in FIGURE l in connection with the details of the driver gear, there is provided a gear hub 21 press-fit on a shaft including a first shaft extension 22 and a second shaft extension 23 extending from opposite side `faces of. the gear hub 21, the side faces being identified respectively at 24 and 26. The shaft extension 23 has a coupling portion 27 adapted to be connected to a suitable prime mover for rotatably driving the pump.

In the closure plate 12 there is provided a bore 28 to receive in press-tit relation a bearing sleeve 29 in order to provide a journal for the shaft extension 22.

The closure plate 12 is also provided with a at surface or wall 30 extending perpendicularly to the axis of the driver gear shaft and forming a side wall to the pumping chamber 17 as well as providing a thrust and sealing surface for the side face 24 of the gear.

In order to provide a bearing surface for the shaft extension 23, the pump cover 13 is also provided with a bore 31 into which is press lit a bearing sleeve 32. A sealing device 33 is mounted in the cover member 13 to effect a seal with the shaft extension 23.

A driven gear 34 mounted on a shaft 36 meshes with the driver gear 21 to provide the tiuid displacement or pumping action and it will be understood that the gear 34 and shaft 36 are mounted within the pump casing similarly in the manner of gear 21.

The cover member 13 has formed thereon a wall surface 37 which extends transversely or radially to the gear shafts and parallel to the gear side faces 26 to provide an interior wall for the pumping chamber 17.

The gear pump illustrated in the drawings generates a pumping action when the meshed gears rotate by receiving liuid between the gear teeth as the teeth of the two gears separate or disengage at the inlet side of the pumping chamber and by expelling such fluid from between the teeth as the teeth begin to mesh or engage on the discharge side of the pumping chamber. Since the fluidfilled spaces between the gear teeth are not completely isolated from adjacent spaces a fluid pressure within the spaces increases continuously as the gear teeth and the spaces therebetween are rotated from the inlet to the outlet side of the pumping chamber.

This variation in liuid pressure around the circumference of the gears makes it desirable to seal the side faces of the gears with sealing forces which vary around the circumference of the gears in accordance with the circumferential variation in fluid pressures generated by the gears.

In addition, during operation of the gear pumps the gears will expand somewhat due to temperature rise and it is desirable that provision be made to allow for expansion in the width of the gears while providing simultaneously the requisite sealing effect on the side faces of the gears.

In accordance with the principles of the present invention, a thin, flexible wear or end plate 38 is interposed between side faces 26 of the gears 21 and 34 and the interior wall 37 of the cover member 13.

The wear plate 38 operates to effectively acmodate expansion of the gears while providing a seal for the side faces of the gears. In order to receive the shafts 23 and 36, the end plate 38 is provided with circular apertures 25, and in order to receive the alignment studs 14 and the fastener members 16, the plate is provided with apertures as at 35. A pair of trapping reliefs 35 and 35a may be formed in the end plate adjacent the area at which the gears 21 and 34 come together in meshing relation.

Further in accordance with the invention, the interior wall 37 against which one side of the wear plate 38 abuts has formed therein a slightly undercut generally ovoidshaped relief portion or recess 39 which is centrally positioned with respect to and which completely surrounds the gear shafts 23 and 36 as viewed in FIGURE 2. The recess 39 is bounded by a side wall 40 having a pair of spaced parallel side portions 41 and 42 connected at opposite ends thereof by semi-circular portions 43 and 44.

That portion of the interior wall 37 surrounding the relief portion 39 forms a sealing surface 46 and has formed forming a tluid collection trough or channel 47 which extends inwardly of the outer margin around the interior wall 37 in registry with a similar channel 48 formed in a facing wall 49 of the center body member 11.

The inlet side of the relief portion 39, that is, that portion thereof which lies adjacent the inlet side 19 of the pumping chamber 17, is separated from the discharge side of the undercut portion by means of a partitioning or gasketing member t), which may be formed of material such as nylon or the like, and which is interposed between the wear plate 38 and the relief portion 39. It will be noted that the gasket member 50 divides the relief portion 39 such that the gasket 50 is generally symmetrical about a plane transverse to the plane within which the axes ot shafts 23 and 36 lie and situated intermediate the two shafts. The gasket 50 is generally arcuately shaped and comprises a pair of end portions 51 and 52 which terminate in grooves as at 53 formed in the sealing surface 46, from which the gasket member 50 extends in a pair of straight leg portions 54 and 56 on opposite sides of the shafts 23 and 36 and at right angles to a line drawn between the axes of the shafts, and then extends concentricalty around portions of the shafts in central portions as at 57 and 58 which join in a reversely curved middle portion 59.

The cross-sectional configuration of the gasket member 50 is generally circular and `that portion thereof that extends into the relief portion 39 in FIGURE 2 is received in a groove 60 which is deeper than the groove 53 formed in the raised surface 46 and which is also deeper than the cross-sectional dimension of the gasket 50.

Another groove 61 is formed in the relief portion 39 and is substantially as deep as and is in open communication with `the groove 60.

As illustrated best in FIGURES 3 and 4, an aperture or tiuid passageway 62 is formed in the flexible wear plate 3S in registry with the groove 61 on the discharge side of the pump. During operation, high pressure fluid in the discharge side of the pumping chamber 17 flows through aperture 62. Such fluid is under a pressure substantially therein a circumferentially continuous loop equal to the discharge pressure of the pump and lls the space between the relief portion 39 and a back or motive surface 63 of the wear plate 38 on the discharge side of the gasket member 50.

In order to prevent leakage of high pressure fluid from the discharge to the suction or inlet side of the relief portion 39, the gasket member is initially subjected to a constant bias against the adjoining surface of the wear plate 38 by means of a generally circularly-shaped resilient biasing member constituted of rubber or the like as indicated at reference numeral 64 housed within the deep groove under the gasket member 5t). The free-state cross-sectional dimension of the biasing member is such that, when added to the cross-sectional dimension or thickness of the gasket 50, the total thickness of the two is greater than the depth of the groove 60 and the depth of the relief portion 39.

When fluid at pump generated pressure is introduced into the groove 60, the gasket member 50 is pressure loaded into abutting engagement with the motive surface 63 of the wear plate 38.

To further enhance the improved balance loading it is further contemplated in accordance with the present invention to communicate areas of the wear plate 38 adjacent the inlet side 19 of the pumping chamber 17 to inlet pressures. For this purpose, another gasketing or sealing member 66 which, in the illustrated embodiment, constitutes an O-ring, is housed in an annular groove 67 formed in the interior wall 37 of the cover member 13 and extending in part in the relief portion 39 and in the sealing surface 46, respectively. An aperture or uid passageway 68 is formed in the wear plate 38 to communicate inlet pressure inwardly of the O-ring 66.

Spaced from the O-ring 66 circumferentially with respect to the gears 21 and 34 are a pair of disc-shaped cavities 69 and 70 formed in the interior wall 37 partly in register with the undercut portion 39 and partly in register with the raised portion 46. Housed respectively within the cavities 69 and 70 are a pair of biasing members as at 71 which, in the illustrated embodiment, constitute O- rings made of rubber or the like material having an overall diameter substantially equal to the diameter of the cavities and having a cross-sectional thickness less than the depth of the cavities.

Also housed in the cavities 69 and 70 in overlying relation with respect to the O-rings 71 `are a pair of annularly shaped discs or buttons as at 72, each having an aperture 73 formed therein centrally thereof and in registry with an aperture 74 formed in the wear plate 38.

During operation of the pump the discs 72, which are constantly biased by means of the O-rings 71 into engagement with the motive surface 63 of the wear plate 38, are biased additionally as a result of uid pressure in the cavities 69 and 70 corresponding with fluid pressures in the pumping chamber 17 adjacent the apertures 74. The remaining portion ofthe recess 39 on the inlet side of the gasket member 50 outside of the ring 66 and the cavities 69 and 70 is under a pressure somewhere intermediate inlet and outlet pressure.

Depending on such factors as, for example, uid viscosity and discharge pressure, a minimal amount of fluid may leak past the sealing surface 46 of the interior wall 37 and into the collection channel 47. Means are provided such as cored passageways in the casing for communicating fluid from the collection channel 47 back to the inlet side of the pump.

In addition, a fluid return chamber 76 is provided in the pump cover member 13 and communicates the bores which receive the shafts 23 and 36 with the suction side of the pumping chamber 17 through a fluid passageway 77 formed in the cover member 13 and the aperture 68 provided in the wear plate 38.

Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim Vas my invention:

l. A gear pump comprising,

a housing having a pumping chamber including an inlet and an outlet,

rotary gears for pumping fluid from the inlet to the outlet,

said casing having a wall on one side of said chamber opposite the adjoining side faces of the gears characterized by a relief recess opposite said pumping chamber and a sealing surface outwardly of said relief recess, an end plate interposed between said gears and said Wall having a sealing face on one side thereof for engaging the side faces of the gears and a motive face on the other side thereof to form a wall of said relief recess,

said end plate having at least one opening opposite the outlet side of the pump for conducting fiuid at pump generated pressure into said relief recess, and an elongated sealing member having its opposite ends clamped between said sealing surface and said motive face at spaced apart points on the inlet side of the pump and having an intermediate section curved through said relief recess on the outlet side of the Pump,

thereby to partition the relief recess into a pressure control zone communicating with said opening to load a corresponding area of said motive face with discharge pressure, and

a reduced pressure zone on the inlet side of the pump.

2. A gear pump as defined in claim 1, wherein said wall has a groove formed therein receiving, positioning and retaining said sealing member.

3. A gear pump as defined in claim 2, and including a resilient gasket in the bottom of said groove and generally coextensive in length therewith to form a continuous biasing means for initially biasing said sealing member against said end plate.

4. A gear pump as defined in claim 3, and including means in said housing for conducting fluid at pump generated pressure into the bottom of said groove to pressure load said sealing member after the pump is in operation.

S. The gear pump as defined in claim 1, wherein said sealing area has a trough-shaped groove formed therein outwardly of said relief recess and communicating with the pump inlet to return any leakage fluid to the pump inlet.

6. A gear pump as defined in claim 1, and including a generally circular sealing means including 'an O-ring sealing member and a groove for receiving same on the inlet side of the pump to form an isolated zone behind said end plate, and means communicating said isolated zone to the pump inlet, thereby to assist in balancing the forces on said end plate.

7. A gear pump as defined in claim 2, wherein said groove formed in said wall has shallow end portions in said sealing surface of less depth than thickness of said sealing member to ensure a good sealing relationship.

8. In a pump,

a housing having means including an interior wall forming a chamber,

rotary fiuid impellers in said chamber having axes extending transversely to said interior wall for pumping fiuid from an inlet, low-pressure side of said chamber to an outlet, high-pressure side,

means in said interior wall forming a recessed relief surface around said impeller axes and forming a sealing surface around the periphery of said relief surface,

a thin fiexible end plate interposed between said interior wall and said impellers `and having one side thereof providing a wear surface for adjoining side faces of said impellers and having an opposite side thereof covering said relief surface and extending over said sealing surface of said interior wall to form a pressure recess between said relief surface and said opposite side,

means clamping said end plate into engagement with said sealing surface,

seal means in said recess to partition said recess into first and second portions adjacent, respectively, said low and said high pressure sides of said chamber, and

fluid passageway means communicating, respectively, said first and said second portions of said recess with said low and said high pressure sides of said chamber to pressurize said recess portions and to urge adjacent portions of said end plate into engagement with the adjoining faces of said impellers in accordance with the pressures in said low and said high pressure sides of said chamber.

9. In apump,

a housing having means including an interior wall forming a chamber,

rotary fluid impellers in said chamber having axes extending transversely to said interior wall for pump. ing fluid from ian inlet,

low-pressure side of said chamber to an outlet, highpressure side,

means in said interior wall forming a recessed relief surface around said impeller axes and forming a sealing surface around the periphery of said relief surface,

a pair of spaced grooves formed in said sealing surface,

a thin fiexible end plate interposed between said interior wall and said impellers and having one side thereof providing a wear surface for adjoining side faces 0f said impellers and having an opposite side thereof covering said relief surface and extending over said sealing surface of said interior wall to form a pressure recess between said relief surface and said opposite side,

means urging said Wear plate into engagement with said sealing surface,

seal means including an elongated gasket member in said recess to partition said recess into first and said second portions adjacent, respectively,

said low and said high-pressure sides of said chamber,

said gasket member having a pair of end portions extending, respectively, into said grooves in said sealing surface, and

fiuid passageway means communicating, respectively,

said first `and said second portions of said recess with said low and said high pressure sides of said chamber to pressurize said recess portions and to urge adjacent portions of said end plate into engagement with the adjoining faces of said impellers in accordance with the pressure in said low and said high pressure sides of said chamber.

10. In apump,

a housing having means including an interior wall forming a chamber,

rotary fluid impellers in said chamber having axes eX- tending transversely to said interior wall for pumping liuid from an inlet, low-pressure side of said chamber to an outlet, high-pressure side,

means in said interior wall forming a relief recess surface around said impeller axes and forming a sealing surface around the periphery of said relief surface,

a thin flexible end plate interposed between said interior wall and said impellers and having one side thereof providing a wear surface for adjoining side faoes of said impellers and having an opposite side thereof comprising a central motive surface covering said relief surface of said interior wall to form a pressure recess and having a peripheral portion extending over said sealing surface of said interior wall,

a pair of spaced grooves of a given depth formed in said sealing surface and opening toward said wear plate,

means clamping said peripheral portion of said end plate into sealing engagement with said sealing surface of said interior wall,

seal means including an elongated gasket member in said pressure recess to partition said recess into first and second portions adjacent, respectively,

said low and said high-pressure sides of said chamber,

said gasket member having a pair of end portions extending, respectively, into said grooves in said sealing surface and having a depth greater than said given depth to abut said end plate, and

fiuid passageway means communicating, respectively, said first and said second portions of said pressure recess with said low and said high pressure sides of said chamber to pressurize said recess portions and to urge corresponding portions of said end plate into engagement with the adjoining faces of said impellers in accordance with the pressure in said low and said highpressure sides of said chamber.

11. ln a pump,

a housing having means including a substantially planar interior wall forming a chamber,

a pair of rotary impellers in said chamber for pumping uid from an inlet side of said chamber to an outlet side,

means in said interior wall forming a relief recess surface extending from said inlet to said outlet side of said chamber and a sealing surface around said relief surface,

a thin flexible end plate interposed between said interior wall and said impellers and covering said relief surface and extending over said sealing surface to form a pressure recess between said relief surface and said end plate,

means clamping said wear plate into engagement with said raised portion,

means partitioning said pressure recess into first and second portions adjacent, respectively, said inlet and said outlet sides of said chamber,

a pair of disc-shaped cavities formed in said interior wall on the inlet side of said partitioning means, a pair of centrally apertured buttons disposed, respectively, in said cavities,

an O-ring in each of said cavities having an outer diameter substantially equal tothe diameter of its respcctive cavity and biasing its respective button against said end plate, and

means forming apertures in said end plate communicating, respectively, said inlet side of said chamber with said disc-shaped cavities and said outlet side of said chamber with said second portion of said pressure recess.

12. In a pump,

a housing having means including a flat interior wall forming a pumping chamber,

a pair of rotatable shafts situated in spaced parallel relation and projecting outwardly from said interior wall,

the axes of said shafts residing in a first plane extending transversely to said interior Wall,

a pair of meshing gears mounted on said shafts for pumping fluid from an inlet, low-pressure side of said chamber to an outlet, high-pressure side of said chamber,

means in said interior wall forming a relief portion surrounding said shafts and having a generally Ovoidshaped outer wall comprising a pair of spaced side portions extending parallel to said first plane and a pair of interfacing arcuately-shaped portions interconnecting the ends of said side portions,

a thin flexible end plate overlying said interior wall to form a pressure recess in said relief portion and abutting adjoining side faces of said gears to provide a Wear surface therefor,

an elongated gasket member completely partitioning said pressure recess into first and second portions adjacent, respectively, said low and said high pressure sides of said chamber,

said gasket member being generally symmetrical about a second plane transverse to said first plane and situated intermediate said shafts and comprising,

a pair of straight leg portions extending, on opposite sides of said shafts in the direction of said first plane, from spaced points on said outer wall of said relief portion at right angles to said first plane,

a pair of central portions extending, respectively, around portions of said shafts in concentric and radially spaced relation thereto, and

a backwardly curved middle portion joining said central portions intermediate said shafts, and

iiuid pnssageways formed in said end plate and communicating, respectively, said first and said second portions of said pressure recess with said low and said high sides of said chamber.

13. The pump as defined in claim 12 and including.

a first groove of a given depth formed in said relief portion and shaped complementarily to said gasket member for receiving said gasket member therein,

said gasket member having a depth less than said given depth, and

a second groove formed in said undercut portion and intersecting said first groove,

said second groove extending away from said lirst groove in said high-pressure side of said chamber and being substantially as deep as said first groove to supply high-pressure fluid to said first groove under said gasket member to urge said gasket member into engagement with said end plate.

14. The claim as defined in claim 13 and including,

a resilient generally cross-sectionally shaped biasing member in said first groove having a free state depth which is such that, when added to the depth of said gasket member, the summation of the two is greater than the summation of the depths of said first groove and said relief portion.

15. In a pump,

a housing having means including an interior wall forming a pumping chamber,

a pair of rotatable shafts situated in spaced parallel relation and projecting outwardly from said interior wall and across said chamber,

the axes of said shafts residing in a plane extending transversely to said interior wall,

a pair of meshing gears mounted on said shafts for pumping tiuid from an inlet, low-pressure side of said chamber to an outlet, high-pressure side of said chamber,

means in said interior Wall forming a relief portion surrounding said shafts and having a generally ovoidshaped outer Wall comprising a pair of spaced side portions extending parallel to said plane and a pair of interfacing arcuately-shaped portions interconnecting the ends of said side portions,

said means also forming a sealin g surface surrounding said relief portion,

a thin flexible end plate overlying said interior wall to form a pressure recess in said relief portion and abutting adjoining side faces of said gears to provide a wear surface therefor,

an elongated gasket member completely partitioning said pressure recess into first and second portions ad jacent, respectively, said low and said high pressure sides of said chamber,

said gasket member comprising a pair of straight leg portions extending, respectively, on opposite sides of said shafts in the direction of said plane, from spaced points on said outer wall on one side of said plane and at right angles to said plane, and a pair of disc-shaped cavities formed in said interior wall along said outer wall on said one side thereof and between and in spaced relation to said spaced points,

said cavities each having a first segment extending into said relief portion and a second segment extending into said sealing surface, a pair of centrally apertured buttons disposed, respectively, in said cavities, an O-ring in each of said cavities having an outer diameter substantially equal to the diameter of its respective cavity and biasing its respective button against said end plate, and means forming apertures in said end plate communicating, respectively, said inlet side of said chamber with said disc-shaped cavities through said central apertures thereof and said outlet side of said chamber with said second portion of said pressure recess. 16. In a pump, a housing having means including an interior Wall forming a chamber, rotary Huid impellers in said chamber having axes extending transversely to said interior wall for pumping fluid from an inlet, low-pressure Side of said chamber to an outlet, high-pressure side, means in said interior wall forming a relief portion around said impeller axes and forming a sealing surface around the periphery of said relief portion,

a thin flexible end plate interposed between said .interior wall and said impellers and having one side thereof providing a wear surface for adjoining side faces of said impellers and having an opposite side thereof covering said relief portion and extending over said sealing surface to form a pressure recess between said relief portion and said opposite side, means urging said end plate into sealing engagement with said sealing portion,

partitioning means in said recess to partition said recess into rst and second portions adjacent, respectively, said low and said high-pressure sides of said chamber,

uid passageway means communicating, respectively, said lirst and said second portions of said recess with said low and said high-pressure sides of said chamber, and

a fluid collection trough formed in said interior wall around said sealing surface for collecting Huid which leaks past said sealing surface and said end plate.

References Cited by the Examiner UNITED STATES PATENTS 2,702,509 2/1955 Garnier 103-126 2,742,862 4/1956 Banker 103-126 2,809,592 10/1957 Miller et al. 103-126 2,990,783 7/1961 Oliver 103--126 3,096,719 7/1963 McAlvay 103-126 3,131,643 5/1964 Marietta 103--126 3,142,260 7/1964 Oliver 103-126 3,145,661 S/1964 Marietta 103-l26 3,171,358 3/1965 Lauck 103-126 MARK NEWMAN, Primary Examiner.

W. I. GOODLIN, Assistant Examiner. 

1. A GEAR PUMP COMPRISING, A HOUSING HAVING A PUMPING CHAMBER INCLUDING AN INLET AND AN OUTLET, ROTARY GEARS FOR PUMPING FLUID FROM THE INLET TO THE OUTLET, SAID CASING HAVING A WALL ON ONE SIDE OF SAID CHAMBER OPPOSITE THE ADJOINING SIDE FACES OF THE GEARS CHARACTERIZED BY A RELIEF RECESS OPPOSITE SAID PUMPING CHAMBER AND A SEALING SURFACE OUTWARDLY OF SAID RELIEF RECESS, AN END PLATE INTERPOSED BETWEEN SAID GEARS AND SAID WALL HAVING A SEALING FACE ON ONE SIDE THEREOF FOR ENGAGING THE SIDE FACES OF THE GEARS AND A MOTIVE FACE ON THE OTHER SIDE THEREOF TO FORM A WALL OF SAID RELIEF RECESS, SAID END PLATE HAVING AT LEAST ONE OPENING OPPOSITE THE OUTLET SIDE OF THE PUMP FOR CONDUCTING FLUID AT PUMP GENERATED PRESSURE INTO SAID RELIEF RECESS, AND AN ELONGATED SEALING MEMBER HAVING ITS OPPOSITE ENDS CLAMPED BETWEEN SAID SEALING SURFACE AND SAID MOTIVE FACE AT SPACED APART POINTS ON THE INLET SIDE OF THE PUMP AND HAVING AN INTERMEDIATE SECTION CURVED THROUGH SAIF RELIEF RECESS ON THE OUTLET SIDE OF THE PUMP, THEREBY TO PARTITION THE RELIEF RECESS INTO A PRESSURE CONTROL ZONE COMMUNICATING WITH SAID OPENING TO LOAD A CORRESPONDING AREA OF SAID MOTIVE FACE WITH DISCHARGE PRESSURE, AND A REDUCED PRESSURE ZONE ON THE INLET SIDE OF THE PUMP. 